The present invention relates to a seal forming method for forming a seal in an end piece of a flexible pipe comprising a pressure sheath, which includes the following steps:                provision, around an end section of the pressure sheath, of a crimping ring that is intended to be introduced into the pressure sheath;        placement, around the end section and the crimping ring, of an end vault of the end piece, the end vault having an engagement surface for engaging with the crimping ring, capable of pushing the crimping ring radially into the pressure sheath;        relative movement of the crimping ring in relation to the engagement surface in order to crimp the crimping ring in the pressure sheath.        
The flexible pipe is advantageously a flexible pipe type that is not bonded (referred to as “unbonded”) intended for the transport of hydrocarbons through a body of water such as an ocean, a sea, a lake or a river. By way of a variant, the flexible pipe line is an umbilical pipe that is reinforced with armor elements or even a cable.
Such a flexible pipe is for example made in accordance with the standard-setting document API 17J (Specification for Unbonded Flexible Pipe) and API RP 17B (Recommended Practice for Flexible Pipe) established by the American Petroleum Institute.
By way of a variant, the flexible pipe is dedicated to applications related to drilling and refinery, bearing the acronym “DRAPS”, manufactured and marketed by the Applicant. This flexible pipe is for example a discharge pipe (per the terminology, known as “choke line”) and a seal-off line (per the terminology, known as “kill line”) as described by the standard-setting document the API 16C established by the American Petroleum Institute.
Preferably, this type of pipe is designed to be disposed in a body of water but it can sometimes be used on land over the mainland.
The pipe is generally formed of an assembly of superposed and concentric, polymer and metallic layers. It is considered to be “unbonded” within the context of the present invention given that at least one of the layers of the pipe is capable of moving longitudinally in relation to the adjacent layers upon the flexion or bending of the pipe. In particular, an unbonded pipe is a pipe that has no bonding materials joining the layers that form the pipe.
The pipe is generally disposed across a body of water, between a bottom assembly, designed for collecting the fluid from the operation at the bottom of the body of water, and a surface assembly that may be floating or fixed, designed for collecting and distributing the fluid. The surface assembly may be a semi-submersible platform, a floating production storage and offloading (FPSO) unit or other type of floating assembly.
Some of these pipes are used in very severe conditions. Thus, the hydrocarbons conveyed may have a pressure and a temperature that are very high, for example a pressure comprised between 500 bar and 1500 bar, and a temperature of between 110° C. and 130° C. In addition, in the event of the pipe being submerged at a great depth, the latter must be capable of withstanding a very high external pressure, for example of the order of 250 bar if the pipe is submerged at a depth of 2500 metres.
In order to respond to such performance requirements, it is a known practice to use pressure sheaths made from high performance polymer materials which preferably have a Young's modulus of at least 2000 MPa, such as, for example PEK (polyether ketone), PEEK (polyether ether ketone), the PEEKK (polyether ether ketone ketone), PEKK (polyether ketone ketone), PEKEKK (polyether ketone etherketone ketone), PAI (polyamide imide), PEI (polyether imide), PSU (polysulfone), PPSU (polyphenylsulfone), PES (polyethersulfone), PAS (polyaryl sulfone), PPE (polyphenylene ether), PPS (polyphenylene sulfide) LCP (liquid crystal polymers), PPA (polyphthalamide) and/or the mixtures thereof, or even in mixture with PTFE (polytetrafluoroethylene) or PFPE (perfluoropolyether).
The use of these materials can cause problems during the forming of the seal around the pressure sheath, during the mounting of the end pieces.
Indeed, during this mounting, a ring is crimped at the level of the external surface of the pressure sheath such as to become embedded therein. The vault of the end piece is pushed axially along the pipe, in a manner such that the crimping ring comes into contact with an inclined surface of the vault of the end piece. This results in a radial pressure or “tube expansion” on the crimping ring, which penetrates radially into the thickness of the pressure sheath. This being done, the pressure sheath is crimped and the sealing is formed.
This operation is easily executable for pressure sheaths made from polymer materials which exhibit a low Young's modulus in the usual temperature range for this type of operation, for example [−10° C.; +40° C.].
However, for certain high-performance polymer materials, the crimping operation is far more complicated. In effect, with their Young's modulus being higher, in the aforementioned temperature range, the crimping is much more difficult.
In order to crimp polymer sheaths made from high performance materials while keeping the same end piece design, it is necessary to use hydraulic devices that generate several tens of tonnes of thrust in order to position the vault of the end piece around the end of the pipe.
The application of such a force may in addition result in the deformation of the metal carcass (in the event of the pipe being of the “rough-bore” type) which can lead to a loss of sealing in the end piece.
An object of the invention is therefore to facilitate the crimping of the pressure sheath during the mounting of the terminal end pieces, in particular when the pressure sheath is made from high performance polymer materials.
To this end, the subject matter of the invention relates to a method of the aforementioned type, characterized in that the method includes, prior to the relative movement step, a step of heating of the end section of the pressure sheath, capable of reducing the Young's modulus of the polymer material of the end section of the pressure sheath and of maintaining a reduced Young's modulus during the relative movement step.
The method according to the invention may include one or more of the following features, taken into consideration in isolation or in accordance with any technically possible combinations:                the Young's modulus of the polymer material of the end section of the pressure sheath, during the step of relative movement, is less than 1000 Mpa, and is in particular comprised between 50 MPa and 500 MPa;        the temperature of the end section of the pressure sheath, during the step of relative movement, is higher than the ambient temperature;        the temperature of the end section of the pressure sheath, during the step of relative movement, is higher than 50° C. and is in particular comprised between 100° C. and 200° C.;        the pressure sheath is made from a polymer material selected from among PVDF, PEK, PEEK, PEEKK, PEKK, PEKEKK, PAI, PEI, PSU, PPSU, PES, PAS, PPE, PPS, LCPs, PPA and/or the mixtures the thereof;        the end section of the pressure sheath is heated from the exterior during the step of heating;        an exterior surface of the end section of the pressure sheath is heated by means of direct contact of a heating member with the pressure sheath and/or with the crimping ring;        the step of placement of the end vault is carried out prior to the step of heating, with the heating step comprising of the heating of the end vault by means of direct contact of the end vault with a heating member, and the heating of an exterior surface of the end section of the pressure sheath through the end vault.        the heating member is a heating strip and/or a heating cover-sheet;        the end section of the pressure sheath is heated from the interior during the step of heating;        the end section of the pressure sheath is disposed around an internal carcass that defines an internal circulation passage for circulating the fluid, the heating step comprising of the heating from the interior of the internal carcass;        the internal carcass is heated by means of a heating mandrel and/or by circulation of hot air in the fluid circulation passage;        a cannula is interposed between a sacrificial sheath arranged around the internal carcass and the intermediate section of the pressure sheath, the cannula being heated in the heating step by the internal carcass, an internal surface of the end section of the pressure sheath being heated by the cannula;        the method as defined here above includes a measurement step of measuring the temperature of the end section of the pressure sheath during the heating step;        the relative movement of the crimping ring in relation to the end vault is a radial movement along an axis of the flexible pipe.        